Method of treating armor-plate.



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SAMUEL S. WALES, 01F MUNHALL PENNSYLVANIA, ASST&NOR T0 CARNEGIE STEELCOMPANY, 015 PITTSBURGH, PENNSYLVANIA, A CQRJPORATION OF NEW JERSEY.

No Drawing.

Specification of Letters Patent.

Patented May f0, 1914.

Application filed November 15, 1906. Serial No. 343,545.

To all whom it may concern:

' Be it known that T, SAMUEL S. WALES, of Munhall, in the county ofAllegheny, State of Pennsylvania, have invented a new and useful Methodof Treating Armor-Plate, of which the following is a specification.

@f recent years it hasbeen the practice in the manufacture of armorplate to make the plate of steel having substantially the followingtheoretical composition :-carbon .28 per cent., manganese .35 per cent.,nickel 3.7 5 per cent., chromium 1.70 per cent., the sulfur and siliconbeing low,-below .04: per cent. The steel of this composition is thentreated by the Harvey or Krupp processes by which its surface is highlysupercarburized for the purpose of rendering it more resistant to theimpact of projectiles. While the rocess of supercarburizing improves thesur "ace it is detrimental in its eflect upon the body of the late.

l have discovered a new composition and a new process of treatment, bywhich I am enabled to make armor plate of homogeneous chemicalcomposition without the necessity of supercarburizing the surface, andmy plate will give much better results in resist- 1n the impact ofprojectiles than have hereto ore been obtained. For example, a sixinchplate which I have made according to my invention, has resisted theimpact of a shell having a velocity 15 to 20 per cent. greater than thatwhich could be resisted by the best Krupp plates of similar thickness.My invention is therefore of great importance, because it enables me toproduce an armor plate having great tenacity and strength, ofhomogeneous composition, and capable of resisting shocks much betterthan any armor plate which heretofore has been produced.

The elements which I alloy with the iron in order to produce my newsteel, are as follows, and in stating. them ll desire to premise that inaddition to those elements, those skilled in the art may add otherelements if desired, or may vary the proportions within certain limits,the proportions which ll give being those which I have heretofore foundbest suited to the purpose: carbon .15 to .25 per cent., manganese .15to .35 per cent.,

- nickel 5. to 12. per cent., chromium .15 to .25

per cent., tungsten .50 to .70 per cent. To these elements ll may addvanadium or molybdenum from .20 to .50 per cent., or T may substitutevanadium or molybdenum in place of tungsten in whole or in part.

Thesteel which if employ is open hearth steel, and l prefer to add thenickel as a part of the charge of the furnace in a cold condition and toadd the manganese, chromium and tungsten in the ladle, or to add them inthe furnace just before tapping, although the time and manner ofaddition may be varied. The proper proportion of carbon is had byrecarburizing in accord ance with usual methods. The silicon content ofthe steel should be as low as possible, say less than .15 per cent. Thesulfur and phosphorus are respectively preferably less than .04 percent.

The new heat treatment to which I subject the steel and which I desireto claim broadly, as Well as in its application to steel having theparticular range of composition stated above, is as follows:-Having castthe ingot and forgedit at the ordinary forging temperature, if it is tobe reforged it is subjected to a heat treatment in which it is raised toa temperature of about 700 degrees C, and cooled slowly, preferably inair. llt may then be reforged at the usual reforging temperature, and isthen heated to a temperature of about 875 degrees (3., which is higherthan that to which the plates are reheated in the Krupp process. It isthen quenched with water, the duration of the water treatment beingprefer- Y ably about one minute per inch of thickness,

the time varying according to the chemical compositlon of the steel,being preferably somewhat less when the carbon content is higher. If thesteel is not reforged, the heating to 875 degrees C. and the quenchingwill immediately follow the forging; the plate not being allowed tobecome cold in the meantime. The steel is then raised to a temperatureabove 710 degrees C. and

erably to about 500 degrees C. by one or more successive treatments, andis allowed plish this water-hardening by a new method, in which I heatthe entire bpdy of the plate uniformly to a temperature of about 725 to775 degrees (1, and then quench it with water applied simultaneously onboth surfaces so as to hardenthe plate uniformly throughout its body. Ithen soften the plate on one surface by heating it on one side only,while the other surface is protected from the heat by loam or otherwise,the temperature being carried preferab'ly to say 500.to 550 degrees C.,the effect of which is to soften one surface of the plate, leaving'theother side with substanti-ally its original hardness. On removing itfrom the furnace I spray the harder surface of theplate in order toprevent the equalization of the heat in the'body of the plate and itssoftening throughout.

Those skilled in the art will be able to modify the steps of the heattreatment above described within certain limits, since What I claimis 1. The herein described method of treating armor plates whichconsists in heating a forged plate to a temperature of about 875 degrees0., then cooling it quickly, again. heating the plate to a temperatureof about 775 degrees C., allowing it to cool slowly, and then annealingthe plate by heatingv to a temperature of about 500 degrees C.

2. The herein described method of treat- 111g armorplate'which consistsin heating the forged plate to a temperature ofabout 700 degrees C.,then re-forging the plate, then heating it to a temperature of about 875degrees C. and quenching, then heating the plate to a temperature ofabout 775 degrees -C and allowing it to cool, then machining the plate,and then re-heating it to a somewhat less temperature than that of thelast re-heating," and forming the plate, thenannealing the plate andmachin- -then hardening the plate ing it, and then water hardening themachined plate. a

3. The herein described method of treating armor plate which consistsin'heat-ing the forged plate to atemperature of about 875 degrees C. andquenching, then heating the plate to a temperature. of about 775 degreesC. and allowing it to cool, then heating the plate to a temperature lessthan 750 degrees C. and forming the plate, and then again heating theplate to about 500 degrees C. and annealing it, then machining theannealed plate, and then water hardening the machined plate.

4. The herein described method of treating plates which consists inheating a forged plate and cooling it quickly, again heating the plateto a somewhat less temperature and annealing, again heating and thenhardening the plate substantially equally throughout, and then applyingheat to one surface of the hardened plate while preventing materialheating of the opposite hardened surface thereof to soften the heatedsurface while maintaining the opposite surface of substantially itsoriginal hardness. r A 5. The herein described method of treating plateswhich consists in heating a forged plate and cooling it quickly, againheating the plate to a somewhat less temperature'a-n'd annealing, againheating and substantially equally throughout, then applying heat to onesurface of the hardened plate while preventing material heating of theopposite hardened surface thereof to soften the heated surface whilemaintaining the opposite surface of substantially its original hardnessand spraying the hardened surface to prevent equalization of thetemperature throughout the plate while air cooling the opposite heatedsurface.

I11 testimony whereof, I have hereunto set my hand.

' SAMUEL s. WALES.

Witnesses CHAS. E. Narornan; IV. H. Comsn'rr.

